Fix some mingw warnings

- Include poppler-config.h for mingw PRINTF_FORMAT
- Only redefine strcasecmp for MSVC
- Recent versions of MSVC have snprintf and vsnprintf
diff --git a/poppler/Error.cc b/poppler/Error.cc
index 99ca3ad..71bd3ce 100644
--- a/poppler/Error.cc
+++ b/poppler/Error.cc
@@ -25,6 +25,7 @@
 //========================================================================
 
 #include <config.h>
+#include <poppler-config.h>
 
 #ifdef USE_GCC_PRAGMAS
 #pragma implementation
diff --git a/poppler/GlobalParams.cc b/poppler/GlobalParams.cc
index 09ad37a..8069b3e 100644
--- a/poppler/GlobalParams.cc
+++ b/poppler/GlobalParams.cc
@@ -82,7 +82,7 @@
 #include <fontconfig/fontconfig.h>
 #endif
 
-#ifdef _WIN32
+#ifdef _MSVC
 #  define strcasecmp stricmp
 #else
 #  include <strings.h>
diff --git a/poppler/PDFDoc.cc b/poppler/PDFDoc.cc
index a2468a5..09ee0a2 100644
--- a/poppler/PDFDoc.cc
+++ b/poppler/PDFDoc.cc
@@ -42,6 +42,7 @@
 //========================================================================
 
 #include <config.h>
+#include <poppler-config.h>
 
 #ifdef USE_GCC_PRAGMAS
 #pragma implementation
diff --git a/test/perf-test.cc b/test/perf-test.cc
index bd45503..7808327 100644
--- a/test/perf-test.cc
+++ b/test/perf-test.cc
@@ -735,15 +735,6 @@
     *root = NULL;
 }
 
-#ifndef _WIN32
-/*static void OutputDebugString(const char *txt)
-{
-    // do nothing
-}*/
-#define _snprintf snprintf
-#define _vsnprintf vsnprintf
-#endif
-
 static void my_error(void *, ErrorCategory, Goffset pos, char *msg) {
 #if 0
     char        buf[4096], *p = buf;
@@ -762,7 +753,7 @@
     }
 
     p = buf;
-    p += _vsnprintf(p, sizeof(buf) - 1, msg, args);
+    p += vsnprintf(p, sizeof(buf) - 1, msg, args);
     while ( p > buf  &&  isspace(p[-1]) )
             *--p = '\0';
     *p++ = '\r';
@@ -785,7 +776,7 @@
 #if 0
     p = buf;
     va_start(args, msg);
-    p += _vsnprintf(p, sizeof(buf) - 3, msg, args);
+    p += vsnprintf(p, sizeof(buf) - 3, msg, args);
     while ( p > buf  &&  isspace(p[-1]) )
             *--p = '\0';
     *p++ = '\r';
@@ -807,7 +798,7 @@
 
     p = buf;
     va_start(args, fmt);
-    p += _vsnprintf(p, sizeof(buf) - 1, fmt, args);
+    p += vsnprintf(p, sizeof(buf) - 1, fmt, args);
     *p   = '\0';
     fprintf(gOutFile, "%s", buf);
     va_end(args);